This invention is relative to the determination of the parameters used to establish with great precision the position of a head gear relative to a cockpit or a seat, while leaving the head completely free to move without creating any significant forces even under high accelerations (high "g" load).
This invention can lead to the development of numerous applications such as in racing cars, tests with mannequins, and on aircraft. This invention can improve significantly the performances of optronic systems such as visual-visor helmet mounted sight or virtual reality visors where the required precision is important.
The current existing systems are heavy, expensive, complex and inaccurate.
The French patent no. 2 672 565 describes a process using an articulated arm composed of articulated segments which include a means to measure the relative position of each segment. In order to obtain a system enabling all possible movements of the head, it is necessary in this case to use a succession of segments (being the structure of the articulated arm and including precise means of measuring the position in space of each segment). This leads to a very complex and expensive system. The mass of this articulated arm creates unacceptable forces under "g" load and especially during front/aft acceleration.
The U.S. Pat. No. 4,062,247 proposes a system connecting the helmet with one point of the cabin. Several means of angle measurements are necessary. The unwinding of two or three bands do not allow, pursuant to this invention, the measurement of neither a length, nor a difference of length. It enables the arm to have a structural rigidity in order to permit the possibility to measure the angle of rotation around the axis 33, 31 23a and 27 of FIG. 1 of this American patent. This system has necessarily a non negligible mass, due to the required rigidity of the band. This mass does create unacceptable forces during "g" loads.
The U.S. Pat. No. 3,867,629 proposes a process enabling the rotation measurement of a solid by using a special polarized surface and complex optronic system. This system requires the usage of sophisticated expensive, unreliable, heavy an inaccurate equipment.
The U.S. Pat. No. 3,917,412 describes a process enabling the measurement of the rotation of the helmet knowing the direction of the emitting sources E1 and E2 from two detectors D1 and D2. This method enables to find the angles positioning the helmet from the angle values. This method necessitates the use of sophisticated technologies that are heavy, expensive, not reliable, and not precise.
The French patent no. 2 433 760 presents an optronical system defining the angular position of a helmet taking into account the local angular position of three points forming a triangle. This system requires sophisticated optical systems which are heavy, complex and expensive.
The French patent no. 2 404 860 presents a system enabling the measurement of the distance of a surface furnishing a diffuse reflection and comprising a light emitting source furnishing a fine beam light, and comprising a beam deviation means in order to create a cycling movement and a light detector. This method requires the usage of sophisticated technologies leading to a high mass, high cost, low reliability, low precision system.
The French patent no. 2 450 463 presents an optical system localising a beam and measuring the direction of this emitting source. Here again the direct measurement of the angles leads to heavy, complex, expensive and inaccurate system.
The French patents no. 2 664 044 and 2 665 415 present a magnetic system incorporated in the helmet and modifying the electro-magnetic field of the cabin according to the position of the helmet. But these systems are very difficult to operate. They are also expensive, heavy, not precise and sensitive to external magnetic fields.
The British patent no. 2 143 948 presents a system comprising a gyroscopic device integrating the accelerations of the helmet and computing the corresponding movements. This system is heavy and expensive and increases the mass of the helmet.
The British patent no. 1 520 154 presents a system determining the position of the helmet comprising at least three points emitting radiation and a fixed part detecting the angular position of these points. This system requires the use of sophisticated technologies which are expensive, unreliable, and not precise.